A Method of Forming a Foam for an Aerosol-Generating Article and a Foam Thereof

ABSTRACT

An improved aeration of foam as well as a method of forming the foam for an aerosol-generating article includes (a) mixing an aerosol-forming agent, a foam-forming agent and optionally a solvent and/or at least one non-tobacco flavoring agent, preferably under heating; (b) adding to the mixture a tobacco-containing agent and/or an inhalable agent; (c) adding a foam-stabilizing agent; (d) cooling of the mixture; wherein the mixture is aerated after the adding of the foam-stabilizing agent and/or after cooling of the mixture, and wherein sodium bicarbonate is added to the mixture before cooling of the mixture, wherein the sodium bicarbonate content is less than 1 wt. % based on the total weight of the foam.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to methods of forming a foam for an aerosol-generating article, comprising a tobacco-containing agent and/or an inhalable agent, an aerosol-forming agent, a foam-stabilizing agent, and a foam-forming agent. This invention also relates to a foam produced by said methods, and foams with a certain improved aeration.

BACKGROUND OF THE INVENTION

Recently different kinds of aerosol-generating articles and its devices for use as a new form of smoking have been mushrooming and commercially available on the market. These include one of the most well-known new form of e-cigarettes that are electrically heated in which an aerosol is generated by the transfer of heat from a heating element of the aerosol-generating device to the aerosol-generating substrates or materials.

It has been reported that in heat-not-burn aerosol-generating articles, aerosol-forming substrate is heated at a rather relatively low temperature, for instance below 350° C., to avoid combustion thereof. A charge of inhalable aerosol can then be released from the aerosol-generating article. The aerosol released is originated from the aerosol formers, which are incorporated into the tobacco material, which may be particulated or granulated.

Tobacco material which has been homogenised is often used in the production of tobacco products. Parts of tobacco plants that are less suited for the production of cut filler such as tobacco stems or tobacco dust are typically materials used for homogenised tobacco material. These reconstituted tobacco can be provided in form of for example powder, sheet or foam (mousse).

Foamed tobacco product, as described, is one example which is known in the prior art mainly in the field of reconstituted tobacco products. Manufacturing processes usually involve forming reconstituted tobacco sheets out of finely ground tobacco particles with a foam-forming agent and a foam-stabilizing agent, followed by shredding the reconstituted sheets, and blending with natural tobacco shreds. The reconstituted tobacco products are usually used for the manufacture of cigarettes.

Reconstituted tobaccos in form of sheet or powder are generally better perceived in the market than the reconstituted tobaccos in form of foam or a mousse because of their textures and consistencies which are closer to the original tobacco materials. Foamed reconstituted tobacco however has its own advantages, for instance, less amount of tobacco-containing material is generally needed to be provided to the aerosol-generating consumables compared to those provided in sheet form or powder form but due to its higher capability of delivery of volatile compounds such as nicotine, less amount of the tobacco-containing material is required to achieve the same result as in other forms such reconstituted tobacco sheet. As a result, lower production cost can be achieved.

It would therefore be desirable to provide an improved method of forming foam for an aerosol-generating article as well as to provide an improved foam which is capable of delivering closer to conventional smoking articles.

SUMMARY OF THE INVENTION

The inventors of the present invention have found solutions to the above-discussed problems through the method of forming a foam for aerosol-generating article and the foam thereof.

A first aspect of the invention is accordingly to provide a method of forming a foam for an aerosol-generating article, comprising the steps of

-   -   mixing an aerosol-forming agent, a foam-forming agent and         optionally a solvent and/or at least one non-tobacco flavoring         agent, preferably under heating;     -   adding to the mixture a tobacco-containing agent and/or an         inhalable agent;     -   adding a foam stabilizing agent;     -   cooling of the mixture;

wherein the mixture is aerated after the adding of the foam-stabilizing agent and/or after cooling of the mixture, and wherein sodium bicarbonate is added to the mixture before cooling of the mixture, wherein the sodium bicarbonate content is less than 1 wt. % based on the total weight of the foam.

A second aspect of the invention is a foam comprising: a tobacco-containing agent and/or an inhalable agent, an aerosol-forming agent, a foam-forming agent, sodium bicarbonate and a foam stabilizing agent,

wherein the weight of the tobacco-containing agent and/or the inhalable agent is 0.1-33 wt. % of the weight of the foam, and

the weight of the aerosol-forming agent is 10-80 wt. %, preferably 40-70 wt. %, of the weight of the foam, and

wherein the weight of the sodium bicarbonate is less than 1 wt. % based on the total weight of the foam.

The inventors have found out that the foam manufactured according to the present invention, thanks to the sodium bicarbonate (NaHCO₃), the foam according to the present invention unexpectedly improves tobacco taste of the aerosol-generating article, improves stability, processability as well as increased pore volume of the foam. According to a series of observations and tests which were carried out, it has been observed that compared to tobacco foam without sodium bicarbonate, foam with sodium bicarbonate has an increased aeration value (pore volume) of the foam/mousse, thus particularly suitable for compact shaped substrates e.g. when the substrate is shaped into different forms such as card, pellet and stick. Moreover, it was found out that the porosity of the foam not only increases significantly and the texture of the product obtained is fluffier, the flavour and aroma of the tobacco, which is highly sought after by the consumer, also increased significantly.

The sodium bicarbonate content is less than 1 wt. % based on the total weight of the foam according to the present invention. Thanks to the sodium bicarbonate which reacts with the mixture, wherein the mixture is preferably acidic, gases such as carbon dioxide is released, and in addition of the aeration of mixture, thus contributing to the increased porosity of the foam.

According to some embodiments, the pH of the mixture is adjusted to a pH value between 5 and 9, e.g. between 5 and 8.5. In other embodiments, acidic condition is preferred, for instance between 4 and 6.9. Such acidic condition enhance the release of carbon dioxide from the reaction of sodium bicarbonate, thus giving an increased pore volume to the foam.

In yet some embodiments, it further comprises a step of adding a binder to the mixture, preferably before the aeration step or before the cooling of the mixture. Binder are used in the present invention to bind fine particles such as tobacco-containing agent and other agents together.

In yet another embodiment, the binder content is less than 15 wt. % based on the total weight of the foam.

According to one preferred embodiment, the sodium bicarbonate content is between about 0.25 wt. and 0.75 wt. % based on the total weight of the foam. The inventors found out that sodium bicarbonate of 0.75 wt. % based on the total weight of the foam generates more open pored foam compared to 0.25 wt. % based on the total weight of the foam. Higher percentage of open pored foam allows increased aeration of the foam, thus improves the vapour released of the tobacco-containing foam.

In one embodiment, the pH of the mixture is adjusted to a pH value between 5 and 9, e.g. between 5 and 8.5.

According to one particular preferred embodiment, the sodium bicarbonate is added a second time to the mixture after the step of cooling the mixture. When an additional amount of sodium bicarbonate (e.g. in total less than 1% of sodium bicarbonate in the total weight of foam) is added after the cooling of the mixture e.g. after at least 6 hours in room temperature (around 22° C.), the sodium bicarbonate reacts better with the cooled (room temperature) mixture by releasing gasses such as carbon dioxide, thereby aerating the foam. An external aeration step could further enhance the aeration of the foam, thereby producing a higher percentage of pore volume of the foam.

According to some preferred embodiments, the foam-stabilizing agent has a viscosity between 300 mPas and 3000 mPas, preferably between 400 mPas and 2500 mPas, further preferably between 500 mPas and 2000 mPas, when measured at room temperature i.e. around 22° C.

According to yet some embodiments, the foam forming agent has a gel strength between 300 g/cm3 and 3000 g/cm3, preferably between 400 g/cm3 and 2500 g/cm3, further preferably between 500 g/cm3 and 2000 g/cm3, and/or wherein the foam-forming agent has a viscosity between 300 mPas and 3000 mPas, preferably between 400 mPas and 2500 mPas, further preferably between 500 mPas and 2000 mPas, when measured at room temperature i.e. around 22° C.

According to yet another embodiment, the foam is extruded and portioned and/or shaped after cooling.

In some embodiments, the foam has a pore volume of at least 5 vol. %, preferably having an aeration of between 12 and 20 vol. %, preferably between 12 and 15 vol. %, more preferably 15 vol. %, based on the total volume of the foam.

In yet another embodiment, the foam-forming agent is a non-protein containing polysaccharide, and the weight of the foam-forming agent is less than 20 wt. % of the total weight of the foam.

According to some preferred embodiment, present invention further comprises a solvent, preferably water, and/or an acid and/or an ester in an amount of up to 15 wt.-%, based on the total weight of the foam, preferably up to 5 wt.-%.

According to one preferred embodiment, the foam is an open pored foam. In other words, more than 50% of the foam are open pored foam i.e. fluidly connected with each other.

In one particularly preferred embodiment, the foam comprises at least 20% of the bubbles in the foam have a diameter between 25 μm and 50 μm, and/or at least 15% of the bubbles have a diameter between 51 μm and 100 μm, and/or at least 11% of the bubbles have a diameter between 101 μm and 171 μm.

According to another embodiment, the foam comprises at least 30% or at least 40% of the bubbles in the foam have a diameter between 25 μm and 50 μm, and/or at least 23% or at least 30% of the bubbles have a diameter between 51 μm and 100 μm, and/or at least 15% or at least 22% of the bubbles have a diameter between 101 μm and 171 μm.

By “about” or “approximately” in relation to a given numerical value, it is meant to include numerical values within 10% of the specified value. All values given in the present disclosure are to be understood to be complemented by the word “about”, unless it is clear to the contrary from the context.

The indefinite article “a” or “an” does not exclude a plurality, thus should be treated broadly.

Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

A tobacco-containing material can be any compound, mixture, particle matter, and/or solution that contains and/or carries a constituent of tobacco, either artificially included or naturally contained in tobacco, e.g. tobacco, tobacco particles, tobacco flavor and/or nicotine. In contrast, an example for an artificially added non-tobacco-specific flavor would be menthol.

As used herein, the term “aerosol-generating article” refers to an aerosol-generating article for producing an aerosol comprising an aerosol-generating material that is intended to be heated rather than combusted in order to release volatile compounds that can form an aerosol.

As used herein, the term “aerosol-generating material” refers to a material, upon heating, capable of releasing volatile compounds, which can form an aerosol. The aerosol generated from aerosol-generating material of aerosol-generating articles described herein may be visible or invisible and may include vapours (for example, fine particles of substances, which are in a gaseous state, that are ordinarily liquid or solid at room temperature) as well as gases and liquid droplets of condensed vapours.

An aerosol-forming agent can be any compound, mixture and/or solution that is capable of forming an aerosol, e.g. when heated and/or in mixture with a tobacco-containing agent. Well known examples include humectants such as glycerin and propylene glycol, other alcohols, such as ethanol, etc.

An open pored foam as used herein is to be understood as a foam which can be considered as being formed of a plurality of interconnecting pores (formed out of a structural material derived from the foam forming agent cooperating with the interacting components such as the foam stabilizing agent, solid components such as tobacco particles and some solvent, etc.) which are able to contain fluid, in particular a mixture of humectant/liquid aerosol-forming substrate and air, wherein at least a significant portion (e.g. greater than 50% by volume) of the pores in the foam are fluidly connected with each other, contrary to a closed-cell foam, wherein the majority of the pores form discrete pockets, each completely enclosed by pore-forming material so as to substantially prevent fluid from passing freely between pores. It is currently believed that the mousses formed as described herein are largely open-pored mousses because after cooling or heating of the aerosol-generating material comprising the sodium bicarbonate, vapour is released from the mousse, substantially all of the humectant appears to be released based on measuring of the weight of the mousse portion before and after heating, which could not be readily explained if the humectant was not able to travel through neighboring pores to reach the surface of the mousse portion. However, alternative explanations cannot be totally excluded—for example closed pores could perhaps be opened by rupturing a closed cell wall as a result of the pressure of vaporized gas, etc.

An electronic cigarette (e-cigarette) or similar devices like electronic pipes or heat-not-burn devices, as referred to in the present invention, are not particularly limited, and may be used to provide a user with an aerosol to inhale. It can, according to certain embodiments, comprise a mouthpiece, a heater, a receiving portion, e.g. a pod, stick, capsule and a casing.

As used herein, wt.-% is to be understood as weight percent, based on the total weight of the foam, unless explicitly otherwise specified. In the present disclosure, all amounts are given in wt.-%, unless clearly stated otherwise or obvious from context. In the present disclosure, furthermore all amounts given in wt.-% add up to 100 wt.-%. The weight percent are thereby calculated by dividing the mass of each component by the total mass e.g. of the foam, unless indicated otherwise or clear from context.

As used herein, vol. % is to be understood as volume percent, based on the total volume of the foam, unless explicitly otherwise specified. In the present disclosure, all amounts given in vol. % in a particular foam add up to 100 vol. % The volume percent are thereby calculated by dividing the volume of each component by the total volume of the foam, unless indicated otherwise or clear from context.

Similarly, aeration values (also known as pore volumes as used herein) indicate the vol. % of the foam or mousse which is composed of air. The actual aeration values of samples have been estimated using the following procedure: a sample of “foam” is made without taking any action (e.g. whipping or aerating with an aeration machine) to aerate the “foam” and a known volume of this unfoamed “foam”/material is measured. Then a sample of the foam made after performing an aeration step (e.g. a step such as whipping or aerating with an aeration machine) and the same known volume of the aerated foam is again weighed and the percentage reduction in the weight is calculated. By assuming that the aeration of the unfoamed material is zero and by assuming that the air has a negligible weight, this directly gives an estimation of the aeration value by assuming that the reduction in measured weight results from replacement of the unfoamed material with (weightless) air. E.g. if the weight is observed to be 4% less for the same volume of foamed material compared to that volume of unfoamed material, then is assumed that 4% of the unfoamed material has been replaced with air, meaning that the vol. % of air is 4%.

Particle sizes, as disclosed in this invention, can be measured by any suitable method, e.g. sieving or laser diffraction, preferably sieving.

The (dynamic) viscosity described herein refers to the flow behaviour of liquids. It is defined as the internal frictional resistance of a liquid to the application of a pressure or a shearing stress. The dynamic viscosity is given in millipascal-seconds (mPas) and is determined by using a rotary viscometer. The viscosity measured in performed at room temperature i.e. 22° C.

As used herein, “cooling” is to be understood as having a temperature at a room temperature (around 22-24 degrees Celsius) for at least 60 minutes, or at a temperature less than 16° C. for at least 10 minutes, or more preferably at a temperature less than 12° C. for at least 5 minutes.

As used herein, “aeration” is to be understood as introduction of air or gasses into, through an external step, into the material. The aeration can be performed for instance though whipping, beating, mixing or aerating with an aeration machine such as Krups Prep & Cook HP 5031 mousse whipping shuffle, or by injection air with an aerator, e.g. like Mondomix aerator. Aeration can be carried out at any suitable temperature. The duration of the aeration can be for instance 1, 2, 3, 4, 5 or 10 minutes or more.

DETAILED DESCRIPTION OF THE INVENTION

Present invention relates to a method of forming a foam for an aerosol-generating article and the foam thereof. It has been found out that when the aerosol-generating tobacco-containing mixture for forming the foam comprises additionally sodium bicarbonate, a significant increase of aeration of the tobacco mousse has been observed. This observation can be attributed by the fact that gasses such as carbon dioxide is released from the foam mixture, more so especially when the mixture is provided in an acidic condition. In other words, the pore volume of the foam increased significantly compared to those foam without having sodium bicarbonate.

Interestingly, this result where the foam produces higher percentage of pore volume is observed only in the foam comprising sodium bicarbonate (NaHCO₃) and less prominent result is observed in the foam comprising sodium carbonate (Na₂CO₃). Without being bound by theory, this phenomenon is likely due to the caustic nature of sodium carbonate, while sodium bicarbonate displays less of that caustic character. Of the two base compounds, sodium carbonate is the stronger base because sodium carbonate is also a diprotic, a term given to something that reacts with two equivalents of acids. After reacting to one equivalent of acid, it then converts to sodium bicarbonate, a monoprotic. For this reason, it is believed that sodium bicarbonate being a weaker basic (alkaline) compound could generate constantly gasses, thereby better aerating the foam. Hence, it is preferably that the sodium bicarbonate is added to the mixture for foam formation in a more acidic condition, for instance having a pH between 5.0 and 6.9.

The foam according to the present invention is particularly suitable to be shaped into compact substrates such as in form of a thin card, pellet or stick. When the foam substrates are being compacted, for instance into a very thin form (˜1 mm), pore volume of the foam becomes crucial as it determines the aeration efficiency of the foam. Existing tobacco foam products are hence not suitable to be compacted as the aeration of the foam/mousse decreases significantly when being compacted.

For this reason, thanks to the sodium bicarbonate, wherein the foam preferably comprises less than 1% of the total weight of the foam, the foam according to the present invention achieves better aeration due to higher pore volume in the foam. This in return increases the release of the vapour/aerosol. To this end, it has been found that the tobacco taste has improved unexpectedly, as the foam is not only more stable and fluffy, but also capable of releasing stronger tobacco flavour and aroma upon heating of the foam. The achieved aeration of the substrate thanks to sodium bicarbonate addition is further advantageous in that it allows to reduce, for a given substrate portion format, the total weight of the substrate portion can be significantly reduced, in practice between 20%-40% lower, compared to a same substrate portion not comprising sodium bicarbonate.

It is disclosed herein that the foams according to certain embodiments are not bound and/or connected to a carrier, i.e. can be used as is, i.e. as free-standing foam. Particularly, the foam are not bound to a substrate according to certain embodiments, but rather are used as is. Thus, according to certain embodiments, the present foams are stable enough to be used as is, i.e. are self-supporting, and have a sufficient stiffness so that they are not bent when picked up on their own and do not require a further stabilizing substrate.

According to certain embodiments, the present foams are biodegradable.

The foam structure in the foams is not particularly limited and can, for example, comprise trapped air bubbles and/or bubbles of other gases such as nitrogen or oxygen, e.g. air bubbles. It can be provided as an open structure with a large surface area, which enables heat and aerosol to circulate through the foam, particularly during heating, thus providing uniform heating, a good quality aerosol, and extremely efficient extraction of the tobacco-containing agent and/or the inhalable agent. According to certain embodiments the foam is an open pored foam. This means that the foam has an open pore structure according to certain embodiments. With an open pored structure, i.e. an open pored foam, circulation of heat and aerosol is enhanced. It can be a liquid foam, a dry foam, a solid foam, or a pellet, preferably a dry foam, a solid foam or a pellet. The foam forming agent generally can trap the bubbles when the foam is formed, e.g. whipped, and the foam stabilizing agent can reduce and even prevent breakdown of the foam.

The bubbles of the foam may have an average diameter in the range of 25-130 μm, e.g. 45-110 μm, e.g. 70-85 μm, and about 97% of the bubbles may have a diameter of 180 μm or less, e.g. 160 μm or less, e.g. 140 μm or less, e.g. 120 μm or less. According to certain embodiments at least 20%, preferably at least 30%, further preferably at least 35% of the bubbles, also possibly referred to as pores, in the foam have a diameter between 30 μm and 55 μm, and/or at least 15%, preferably at least 25%, further preferably at least 30% of the bubbles have a diameter between 51 μm and 100 μm, and/or at least 15%, further preferably at least 20% of the bubbles have a diameter between 101 μm and 171 μm.

The diameter therein can be determined e.g. using a microscopy method, e.g. using a Digital Microscope VHX Keyence. However, the method of determining the bubble size is not particularly restricted. The foam may be formed into any suitable shape for insertion into an e-cigarette. According to certain embodiments, the present foam comprises at least one blind or hole through the foam for circulation and aerosol transmission, e.g. one, two, three, four, five, six, seven, eight, nine, ten or more hole through the foam.

An example shape is an annular pipe shape hole going through the foam portion of any shape, e.g. of about 1 cm diameter, e.g. a 3 mm through hole, or a square, a star, but can also be any other shape or dimension. According to certain embodiments, the foam is having a structure having a big surface area, e.g. having at least one surface with at least one distance between any two sides of the surface or with a diameter that is sufficiently larger than the thickness of the foam. The foam can thus be in the shape of a disc, e.g. a cylindrical disc, a thin plate, etc. According to certain embodiments the at least one hole is going through the at least one surface with at least one distance between any two sides of the surface or with a diameter that is sufficiently larger than the thickness of the foam.

In the present invention, the foam-stabilizing agent is not particularly limited as long as it can stabilize the foam to some extent after formation. According to certain embodiments, the foam stabilizing agent of the present foam is selected from the group consisting of cellulose gum, hydroxyalkylated carbohydrates, and mixtures thereof. Both of the cellulose gum and the hydroxyalkylated carbohydrates are not particularly restricted. According to certain, preferred, embodiments, the foam-stabilizing agent is a cellulose gum, particularly a carboxymethylcellulose, or a derivative thereof. An exemplary, preferred, cellulose gum which may be used in the present invention is CEKOL® 2000 and/or Ceroga 4550C (C. E. Roeper GmbH), a purified sodium carboxymethylcellulose each. Another class of suitable foam stabilizing agents are hydroxyalkylated carbohydrates, and more preferably cellulose ethers and derivatives thereof. A cellulose ether or derivative thereof that can be used can have at least one substituent selected from the group consisting of methyl, ethyl, hydroxyethyl and hydroxypropyl groups. It can further be substituted with a linear or branched substituted or unsubstituted alkyl radicals having 1-20 carbon atoms or an aralkyl radical having 7 to 20 carbon atoms. Such radical is preferably attached by an ether linkage. Suitable substituents can e.g. a hydroxy group, a carboxy group with 1 to 4 carbon atoms, etc. According to certain embodiments the cellulose ether is selected from hydroxyethylcellulose, methylcellulose, methylhydroxyethylcellulose, ethylhydroxyethylcellulose, and mixtures thereof. Furthermore, mixtures of different cellulose gums, different hydroxyalkylated carbohydrates, and mixtures of one or more cellulose gum with one or more hydroxyalkylated carbohydrate, as well as derivatives of one or either thereof, can be used. Also included as derivatives are salts of these cellulose ethers, preferably alkali metal salts thereof, e.g. sodium and/or potassium salts thereof.

Also the foam-forming agent is not particularly restricted. According to certain embodiments, the foam-forming agent of the present foam is selected from the group consisting of agar, gellan gum, lecithin, polyglycerol esters of fatty acids, glycerol esters of fatty acids, sorbitan esters of fatty acids, and/or mixtures thereof, without being limited thereto. A preferred foam-forming agent is gellan gum. Glycerol esters can be prepared by standard esterification methods. If glycerol esters of fatty acids are used, the foam-forming agent can suitably be a compound such as glycerol monostearate and/or glycerol monooleate. Polyglycerol esters can be prepared by polymerizing glycerin under alkaline conditions suitably followed by reacting them with specific fatty acids. Suitable polyglycerol esters can be hexaglycerol monooleate, octaglycerol monostearate and/or octaglycerol monooleate. Sorbitan esters of fatty acids used in certain embodiments of the present invention can be sorbitan monostearate, sorbitan monooleate and/or sorbitan mono palmitate. Furthermore, any possible combinations of compounds belonging to the above mentioned classes can be used.

The present methods are characterized in that the mixture is aerated after adding of the foam-stabilizing agent and sodium bicarbonate and/or after cooling of the mixture. This does not exclude that other aeration steps are also being carried out, and according to certain embodiments, one, two or preferably all of the optional aeration steps are carried out in the present methods. Also it is not excluded that aeration is carried out already concomitantly with a mixing and/or addition step.

The method of aeration is not particularly restricted and can involve e.g. an injection of air, a whipping in of air—e.g. a mixing with a sufficiently large paddle/shuffle and/or a sufficient paddle movement and/or at sufficient lower speed so that air can be introduced into the mixture, bubbling air through the mixture, etc. For example, aeration can be carried out using a sufficient mixing machine similar to a mixer for preparing a mousse, e.g. a Krups Prep & Cook HP 5031 mousse whipping shuffle, and or by injection air with an aerator, e.g. like Mondomix aerator. Aeration can be carried out at a suitable temperature, e.g. at room temperature (around 20-24° C.), 30-80° C., e.g. to 35-75° C., preferably between and including 30-60° C. In the present methods it is not excluded that aeration is carried out concomitantly with a mixing and/or in a step of adding an ingredient, e.g. when using whipping.

In the present invention, ingredients for forming the aerosol-generating foam such as the aerosol-forming agent, the form-foaming agent, the foam-stabilizing agent, the tobacco-containing agent, the inhalable agent, the at least one non-tobacco flavoring agent, sodium bicarbonate and the solvent are not particularly restricted. Also a gas used for aeration is not particularly restricted, and can be e.g. air. Also further components can be admixed. According to certain embodiments, essentially no further components or no further components are admixed, though.

Propylene glycol as used in the present invention is to be understood as propane-1,2-diol. Glycerin or glycerol as used in the present invention is to be understood as 1,2,3-propanetriol.

The aerosol forming agent can further comprise water. According to certain embodiments, no water is contained, though, since water in aerosol form can burn the mouth of a user. Water can be contained in an amount of 0-15 wt.-% of the weight of the foam, e.g. 5-10 wt.-%.

EXAMPLES Example 1

The present invention will now be described in detail with reference to examples thereof. However, these examples serves merely as illustrative purpose and do not limit the scope of the invention.

TABLE 1 Components used in different sodium bicarbonate percentage. Tobacco Mousse (TM) Com- Sample pounds Sample 1 Sample 2 Sample 3 4 Propylene  25.0 wt.- %  25.0 wt.- %  25.0 wt.- % 25.0 glycol wt.- % (PG) Glycerin  25.0 wt.- %  25.0 wt.- %  25.0 wt.- % 25.0 (G) wt.- % Sodium    0 wt.- %  0.25 wt.- %   1.0 wt.- % 2.0 bi- wt.- % carbonate Purified   2.0 wt.- %   2.0 wt.- %   2.0 wt.- % 2.0 Water wt.- % Tobacco  34.0 wt.- %  33.75 wt.- %  33.0 wt.- % 32.0 Powder wt.- % Gum   4.0 wt.- %   4.0 wt.- %   4.0 wt.- % 4.0 wt.- % Binder  10.0 wt.- %  10.0 wt.- %  10.0 wt.- % 10.0 wt.- % Total 100.00 wt.- % 100.00 wt.- % 100.00 wt.- % 100.00 wt.- %

Table 1 shows tobacco mousse comprising different percentage of sodium bicarbonate were investigated. For producing exemplary foams, the ingredients given in the respective column of Table 1 were mixed and combined as follows.

Firstly, the propylene glycol, the glycerin and the purified water were whipped and aerated for 5-10 min at 45° C. using a Krups Prep & Cook HP5031 mousse whipping shuffle. When whipping up the mousse, the speed has to be adjusted so that the volume visibly increases and small bubbles appear and partly stay in the foam. If whipping is too fast then mixing will take over and the foamy structure is going to collapse, thus back to fluid. As one option, whipping is started slowly and the whipping speed is slowly increased as the foam begins to develop a lighter, more mousse-like texture; the speed is backed-off by about 10% if it is noticed that the mousse seems to be reducing its mousse-like texture and becoming seemingly less aerated. In order to preserve the foamy structure for creating the stable portion, a sudden cooling with ice or cool water is recommendable. Using the above mentioned Krups device, the best results can be obtained with a speed in between 60 and 200 rpm. Adaptation is within the skilled person's knowledge in accordance with the above description.

In a next step, the gum was added and the mixture was whipped and aerated for 5-10 minutes. Afterwards the tobacco powder was added and whipping and aeration were carried out for 5-10 min. The binder was added and the mixture was again whipped and aerated for 5-10 min. Afterwards the sodium bicarbonate with the desired percentage was added and the mixture was again whipped anf aerated for 5-10 min. Finally the mixture was cooled to 10° C. within 10 minutes and aged at 45° C. or at room temperature for 8 hours.

TABLE 2 Pore volumes (Aeration values) measured from different samples. Tobacco Mousse (TM) Compounds Sample 1 Sample 2 Sample 3 Sample 4 Pore volume 5% 12% 15% 7%

Results obtained from the Example 1 were shown in the Table 2. The samples 2, 3 and 4 which comprised sodium bicarbonate in the mixture showed higher pore volumes or aeration values compared to the control sample (sample 1). Sample 3 which contained 1% of sodium bicarbonate showed the highest increased of pore volume (12%). It is however noted that higher percentage of sodium bicarbonate (2%) in the mixture did not give higher aeration values as expected. For this reason, it is preferably to have one percent or less than 1% of sodium bicarbonate in the foam mixture.

In general, Samples 2 and 3 achieved a good puff impact and smooth, nice tobacco sweetness when heating at 245° C. with 20 s until the first dry puff using an aerosol generation apparatus, Sample 3 in comparison of the Sample 2 achieved a bit higher sweetness, and had a higher impact.

A maximum binding force can be created by suitably increasing the reaction time toward thermodynamic equilibrium. The time to achieve equilibrium is determined by kinetic effects which seem to be dependent on the product temperature mainly in the aging and binding process step. The temperature settings also can relate to the level of volatility of flavors to keep suitable tobacco mousse heating properties. Such as vapor release and flavor release, creating a distinguished taste and smell.

Example 2

The process was carried out as in Example 1, except that mixing and aeration were carried out with an aerator, Mondomix at 3000 rpm. Again, an aeration of 5-20% was achieved. Also aeration with increased pressure of 2.5 bar as counter pressure (30 mm VA) did not increase this level.

Examples 3 and 4

Samples 2 and 3 as in Example 1 were produced in the same way, except that sodium carbonate were added into the foam instead of the sodium bicarbonate, e.g. together with tobacco, reducing the amount of tobacco accordingly. Less aeration values (6% and 8%, respectively) were achieved compared to the Samples 2 and 3 in the Example 1. 

1. A method of forming a foam for an aerosol-generating article, comprising mixing an aerosol-forming agent and a foam-forming agent to create a mixture; adding to the mixture a tobacco-containing agent and/or an inhalable agent; adding a foam-stabilizing agent; and cooling the mixture; wherein the mixture is aerated after the step of adding the foam-stabilizing agent and/or after the step of cooling the mixture, and wherein sodium bicarbonate is added to the mixture before the step of cooling the mixture, wherein the sodium bicarbonate content is less than 1 wt. % based on a total weight of the foam.
 2. The method according to claim 1, wherein the sodium bicarbonate content is between about 0.25 wt. and 0.75 wt. % based on the total weight of the foam.
 3. The method according to claim 1, further comprising a step of adding a binder to the mixture.
 4. The method according to claim 4, wherein the binder content is less than 15 wt. % based on the total weight of the foam.
 5. The method according to claim 1, wherein the foam-stabilizing agent has a viscosity between 300 mPas and 3000 mPas.
 6. The method according to claim 1, wherein the foam-forming agent has a gel strength between 300 g/cm³ and 3000 g/cm³, and/or wherein the foam-forming agent has a viscosity between 300 mPas and 3000 mPas.
 7. A foam comprising: a tobacco-containing agent and/or an inhalable agent, an aerosol-forming agent, a foam-forming agent, sodium bicarbonate, and a foam stabilizing agent, wherein a weight of the tobacco-containing agent and/or the inhalable agent is 0.1-33 wt. % of a weight of the foam, wherein a weight of the aerosol-forming agent is 10-80 wt. % of the weight of the foam, and wherein a weight of the sodium bicarbonate is less than 1 wt. % based on the total weight of the foam.
 8. The foam according to claim 7, wherein the weight of the sodium bicarbonate is between 0.25 wt. % and 0.75 wt. % based on the total weight of the foam.
 9. The foam according to claim 7, wherein the foam has a pore volume of at least 5 vol. % based on the total volume of the foam.
 10. The foam according to claim 7, wherein the foam-forming agent is a non-protein containing polysaccharide, and a weight of the foam-forming agent is less than 20 wt. % of the total weight of the foam.
 11. The foam according to claim 7, further comprising a solvent and/or an acid and/or an ester in an amount of up to 15 wt.-% based on the total weight of the foam.
 12. The foam according to claim 7, wherein the foam is an open pored foam.
 13. The foam according to claim 7, wherein at least 20% of bubbles in the foam have a diameter between 25 μm and 50 μm, and/or at least 15% of the bubbles have a diameter between 51 μm and 100 μm, and/or at least 11% of the bubbles have a diameter between 101 μm and 171 μm.
 14. The foam according to claim 7, further comprising a binder, wherein the binder content is less than 15 wt. % based on the total weight of the foam.
 15. The method according to claim 1, wherein the step of mixing includes mixing a solvent and/or at least one non-tobacco flavoring agent into the mixture.
 16. The method according to claim 1, wherein the step of mixing is carried out under heating.
 17. The foam according to claim 7, wherein the foam has an aeration of between 12 and 20 vol. % based on the total volume of the foam. 